Arc welding operations are known to produce undesirable fumes during the welding process, many of them, such as certain oxides of nitrogen and carbon, being particularly noxious to the welder or others in the vicinity of the welding operation. Such fumes when allowed to accumulate in confined spaces have long been known to constitute a safety hazard, as well as an interference to welder visibility and general welding operation efficiency.
Fume extraction devices commonly have been employed to remove the fumes from the welding area to overcome the above-noted difficulties. Such devices comprise a dual conduit, with one conduit containing the conventional components of the welding apparatus and the other conduit providing a passageway for extraction of the undesirable fumes. The conduits may be formed concentrically.
In such concentric structures, the gun head is provided with an outer sleeve which is slidable axially of the head to alter the degree of suction applied to the welding site. This arrangement is not satisfactory, in that the outer sleeve often becomes detached, and then mislaid, so that the gun loses its effectiveness.